infinite

I am trying to define a function that accepts a point (x,y) as input, and returns an infinite list corresponding to recursively calling P = (u^2 − v^2 + x, 2uv + y) The initial values of u and v are both 0. The first call would be P = (0^2 - 0^2 + 1, 2(0)(0) + 2) = (1,2) Then that resulting tuple (1,2) would be the next values for u and v, so then it would be P = (1^2 - 2^2 + 1, 2(1)(2) + 2) = (-2,6) and so on. I'm trying to figure out how to code this in Haskell. This is what I have so far: o :: Num a =>(a,a) -> [(a,a)] o (x,y) = [(a,b)| (a,b)<- [p(x,y)(x,y)]] where p(x,y)(u,v) = ((u^2)-(v^2)

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Does anyone know if there's a standard class for an infinitely nestable dictionary in Python? I'm finding myself repeating this pattern: d = defaultdict(lambda: defaultdict(lambda: defaultdict(int))) d['abc']['def']['xyz'] += 1 If I want to add "another layer" (e.g. d['abc']['def']['xyz']['wrt'] ), I have to define another nesting of defaultdicts. To generalize this pattern, I've written a simple class that overrides __getitem__ to automatically create the next nested dictionary. e.g. d = InfiniteDict(('count',0),('total',0)) d['abc']['def']['xyz'].count += 0.24 d['abc']['def']['xyz'].total +=

I have an ImageView on which I have applied a rotate animation. Since I want the rotation to go on continuously, I gave the repeatCount as infinite in my rotate.xml: android:repeatCount="infinite" In onCreate(), I load the animation and start it. Animation myAnim = AnimationUtils.loadAnimation(this, R.anim.rotate); objectImg.startAnimation(myAnim); When a button is pressed, the rotation must stop. Hence in my onClick(), I called clearAnimation(). objectImg.startAnimation(myAnim); My simple question is whether stopping the animation is the right thing to do. I assume clearAnimation()

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It's possible to create an infinite nested list in Python. That's clear and, although not popular and definitely not useful is a known fact. >>> a = [0] >>> a[0] = a >>> a [[...]] >>> a[0] == a True My question is, what is happening here: >>> a = [0] >>> b = [0] >>> a[0], b[0] = b, a >>> a [[[...]]] >>> b [[[...]]] >>> a == b Traceback (most recent call last): File "<stdin>", line 1, in <module> RuntimeError: maximum recursion depth exceeded in cmp >>> a[0] == b True >>> a[0][0] == b Traceback (most recent call last): File "<stdin>", line 1, in <module> RuntimeError: maximum recursion depth

I have issues with the following passage from Learn You A Haskell (Great book imo, not dissing it): One big difference is that right folds work on infinite lists, whereas left ones don't! To put it plainly, if you take an infinite list at some point and you fold it up from the right, you'll eventually reach the beginning of the list. However, if you take an infinite list at a point and you try to fold it up from the left, you'll never reach an end! I just don't get this. If you take an infinite list and try to fold it up from the right then you'll have to start at the point at infinity, which

I am constantly getting this error. I am sure the matrix does not have any non-numeric entries. I also tried imputing the matrix, did not work. Anyone know what the error might be? fileUrl <- "https://dl.dropboxusercontent.com/u/76668273/kdd.csv"; download.file(fileUrl,destfile="./kdd.csv",method="curl"); kddtrain <- read.csv("kdd.csv"); kddnumeric <- kddtrain[,sapply(kddtrain,is.numeric)]; kddmatrix <- as.matrix(kddnumeric); svd1 <- svd(scale(kddmatrix)); You have columns composed of all zeroes. Using scale on a column of all zeroes returns a column composed of NaN . To solve this, remove